Systems capable of receiving FM radio signals and decoding embedded metadata may provide additional information about a received broadcast, or about other receivable broadcasts. Such supplemental data is typically broadcast in accordance with the RDS standard (for Radio Data System, as it is known in Europe; the North American standard is known as the Radio Data Broadcast System, however both are customarily referred to as RDS).
Broadcast signals are typically transmitted at fixed intervals within a broadcast spectrum. In the United States, FM signals are usually broadcast at 200 kHz intervals, while in most of Europe the usual interval spacing is 100 kHz. The standard for RDS data transmission reflects this spacing, and RDS decoding systems are typically configured to permit the receipt of data at the expected 100 or 200 kHz intervals.
Many broadcast systems are capable of transmitting supplemental data associated with conventional radio broadcasts. This supplemental broadcast data may provide a receiving system with additional information about a received broadcast program or about other receivable broadcast signals. Examples of such systems are the Radio Data System (RDS) in Europe and the related Radio Broadcast Data System (RBDS) in North America. Such supplemental data can include information such as: a program identifier (PI, or program identification) describing the program being broadcast, which may also be used to identify the geographical availability of the program; the program service name (PS, or program service name, typically the call letters of a broadcast station); the genre or program type (PTY, or program type); an alternate frequencies list (AF, or alternative frequencies list); whether TRAFFIC condition announcements are being broadcast at a given time (TA, or traffic announcement flag) or are generally available on a frequency (TP, or traffic program flag); the time of day (CT, or clock time and date); a free text area left to the discretion of the transmitter (RT, or radiotext); traffic data which permits a display of traffic conditions (TMC, or traffic message channel); information about other stations (EON, or enhanced other networks information); information about the country of origin of the transmission (ECC, or extended country code); the program item number (PIN, or program item number), permitting the unique identification of a specific program by its PI and PIN; data about the content and encoding of an audio signal, such as whether music or speech is being broadcast (MS, or music speech switch); and/or data permitting the receiving system to switch individual decoders on or off, or to indicate whether the PTY code is dynamic (DI, or decoder identification).